Method and apparatus for storing energy and multiplying force to pressurize a downhole fluid sample

Abstract

A method and apparatus store energy in an energy storage medium located in an energy storage chamber. As a sampling tool descends into the borehole, the energy storage medium is pressurized with hydrostatic pressure. A sample is collected in a sample chamber by pumping formation fluid into the sample chamber against hydrostatic pressure. The energy storage medium applies the energy stored in the energy storage medium to the sample through a pressure communication member. A pressure multiplier member increases the pressure applied on the sample by the energy storage medium through the pressure communication member to keep pressure on the sample. A biasing water pressure is applied to the sample at the surface so that the energy storage chamber can be removed from the sample chamber.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This patent application claims priority form U.S. provisional patent application Ser. No. 60 / 618,378 filed on Oct. 13, 2004 entitled A Method and Apparatus For Storing Energy and Multiplying Force to Pressurize A Down Hole Fluid Sample, Shammai et al., which is hereby incorporated by reference in its entirety.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates generally to the field of downhole sampling analysis and in particular to storing energy in a storage medium to pressurize a formation fluid sample at down hole pressure and temperature to retrieve the sample to the surface without significant pressure loss on the sample due to a reduction in temperature. [0004] 2. Background Information [0005] Earth formation fluids in a hydrocarbon producing well typically contain a mixture of oil, gas, and water. The pressure, temperature and volume of the formation fluids control the phase relation...

AI Technical Summary

Benefits of technology

The present invention provides a method and apparatus for pressurizing an object material such as a formation fluid sample. The apparatus includes an energy storage medium that provides a pressure to the object material through a pressure communication member. A force multiplier member is used to multiply the pressure from the energy storage medium to the object material through the pressure communication member. The energy storage medium stores the pressure as the sample is pumped into the sample chamber and the pressure is reduced as the sample is collected. The stored energy is then applied to the sample through the force multiplier member to pressurize it. The invention allows for the efficient and safe pressurization of samples during drilling operations.

Problems solved by technology

Temperatures downhole in a deep wellbore often exceed 300 degrees F. When a hot formation fluid sample is retrieved to the surface at ambient temperature, the resulting drop in temperature causes the formation fluid sample to contract.

A pressure drop in the sample causes undesirable changes in the formation fluid sample characteristics, and can allow phase separation to occur between the formation fluid and gases entrained within the formation fluid sample.

Phase separation significantly changes the formation fluid sample characteristics and reduces the ability to properly evaluate the properties of the formation fluid sample.

Thus, the over pressure supplied to the formation fluid sample in the above related sampling techniques is limited by the capacity of the pump or initial pressure of the gas to maintain the sample at single phase conditions (above the bubble point).

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